Without repeating in detail the description of the machine of the White Patent, it will be recalled here that the fodder is gathered up from the ground by a lifting cylinder or pickup, then introduced and precompressed within a precompression channel opening out laterally into a baling chamber where a baling plunger moves in reciprocating motion.
When the baling plunger moves back, a feeding mechanism transfers the charge present in the precompression channel into the baling chamber. The transfer time corresponds to the short return time of the piston, with the result that the feeding mechanism operates at high speed.
The feeding mechanism conventionally comprises a series of fingers which penetrate slots extending over the length of the precompression channel and sweep this channel under the action of an eccentric drive.
The efforts developed in this mechanism reach a maximum when the feeding fingers penetrate the precompression channel and begin to push the charge.
Consequently, when the resistance exerted by the charge exceeds a critical value, the efforts in the feeding mechanism exceed the threshold of rupture of an element designed as sacrificial element in order to preserve the integrity of the rest of the mechanism.
Of course, the resistance exerted by the charge depends in the first place on the rate of precompression attained in the precompression channel. However, it has been ascertained that this resistance increases sharply when the rate of hygrometry of the cropped material increases beyond a certain threshold, without the causes of such a sharp increase being clearly elucidated.
In a first analysis, the fact of exceeding a certain threshold of hygrometry results in a coalescence or packing of the cropped material, as well as adhesion thereof against the walls of the precompression channel.